Various Improvements to our Docker build

[KevinMind]

Description

While investigating/implementing several issues that rely on our docker build setup:

• Merge requirements.txt files #9461
• Automate l10n extract/merge #5872

I found various improvements that can be made to our docker build setup. These improvements can be split into 2 categories:

• incremental improvements
• step-wise improvements

Where the former are small improvements to the speed or bandwidth requirements of the existing overall build strategy, and the latter are larger architectural changes which imply both bigger gains and bigger cost, risk, etc.

This issue is aiming to track PRs for the former. These are changes which we can safely ship today without seriously risking our overall production/ci/local development pipeline.

### Tasks
- [x] Verify docker image in CI
- [ ] Split docker build into cache efficient stages
- [ ] Extract dev/prod/build apt dependencies per stage.
- [ ] https://github.com/mozilla/addons-server/issues/22060
- [x] Merge requirements files
- [x] Parallelize locale compilation
- [ ] Verify node/npm/python/pip versions are correct regardless of environment
- [ ] https://github.com/mozilla/addons-server/issues/21940
- [ ] https://github.com/mozilla/addons-server/issues/21955
- [ ] https://github.com/mozilla/addons-server/issues/21981
- [ ] https://github.com/mozilla/addons-server/issues/21997
- [ ] https://github.com/mozilla/addons-server/issues/22073

┆Issue is synchronized with this Jira Task

[KevinMind]

Some resources:

• https://github.com/vinodsai-a/github-reusable-workflow-sample/tree/main/actions
• https://docs.docker.com/build/ci/github-actions/cache/
• https://dev.doroshev.com/blog/docker-mount-type-cache/
• https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/reference.md#run---mounttypecache

[KevinMind]

Issues with caching buildkit

• Allow controlling cache mounts storage location moby/buildkit#1512
• --mount=type=cache not caching properly? docker/build-push-action#716

[diox]

https://docs.docker.com/build/guide/mounts/

[KevinMind]

https://docs.docker.com/build/guide/mounts/

Is there something specific to see here, or just wanting to link the documentation?

[diox]

Sorry I just wanted to link to the docs about --mount somewhere for reference - and I didn't want to edit your own comment.

[KevinMind]

Bug with COPY over caching moby/moby#33107

[KevinMind]

docker/build-push-action#225

[KevinMind]

Old Jira Ticket: https://mozilla-hub.atlassian.net/browse/ADDSRV-802